The principal investigator is applying for research support for studies of the digestive enzyme, lingual lipase, which is secreted by the von Ebner glands in many mammalian species, including man. This lipase hydrolyzes dietary triglyceride optimally at pH 4-5. Lingual lipase may have importance in the initiation of fat digestion in the stomach in health, and a compensatory quantitative role in fat digestion both in the neonatal period and in pancreatic insufficiency when intraluminal levels of pancreatic lipase are low. The long-range goals of this work are to characterize rat lingual lipase and to investigate its physiological significance. The aims of this project include: 1. Purification of lingual lipase using immunoaffinity chromatography. Polyclonal antibodies to lingual lipase will be raised in rabbits and also utilized for an enzyme linked immunosorbent assay (ELISA) of lingual lipase concentration. 2. Examination of the stability of lingual lipase in vivo using I25 I-labelled lingual lipase. 3. Physiological experiments on neurohormonal control of lingual lipase secretion in vivo and in vitro acinar preparations of lingual serous glands. 4. Immunocytochemical localization of neuromodulators present in the lingual serous glands and nerve stimulation studies in vivo to establish which neural inputs are important for secretion of lingual lipase. 5. The effects of various diets (i.e. high fat content) on lingual lipase secretion in vivo and the quantitative contribution of lingual lipase in fat digestion will be determined after production of various fistulae (i.e. pancreatic, gastric, etc). We hypothesize that lingual lipase has a particularly important physiological role in fat digestion in conditions when intraluminal pancreatic lipase levels are reduced.